The present invention relates generally to speed reducers especially suitable for use with proportioning pumps and more particularly is directed to a threaded, precise adjustment suitable to substantially eliminate backlash in a worm gear speed reducing drive.
In the field of proportioning pumps and metering pumps, it is now the common practice to provide a motor driven input shaft to drive a speed reducing system which is generally fabricated of the single enveloping worm gear or double enveloping worm gear type. Exemplary of such pumps are the proportioning pumps manufactured and sold by Jaeco Pump Company, West Conshohocken, Pa., 19428 under the designation or style "Jaecopak" and "Jaecofram". The Jaeco Pump Company pumps are suitable for heavy duty metering and comprise essentially a speed reducer of the single enveloping worm gear type which receives input power from an electric motor. Output power is transferred from the input shaft to an output shaft through meshing gear which is conventionally driven by the worm which is affixed to the input shaft. The speed reducer housing of the proportioning pump of the type described is equipped with an open end cap through which the input shaft is rotatively carried through a conventional oil seal. Suitable bearings are positioned interiorly of the speed reducer housing and may be secured to the gear reducer housing by the use of a sleeve in one end and a screwed adjustor on the other end to rotatively carry the input shaft in a manner compensating for backlash, vibration, chatter and thrust loads.
The prior art of proportioning pumps have included gaskets or shims which were installed intermediate one or both end caps and the housing to facilitate adjustment and alignment of the gear relative to the worm by precisely positioning the axial alignment of the input shaft relative to the speed reducer housing. In view of the general type service characteristic of proportioning pumps, wherein one or a pair of pistons or diaphragms are reciprocated by the output shaft, reciprocating or cyclical loads are imposed upon the system. Substantially zero backlash between the worm and gear was absolutely necessary because of the reciprocating nature of the load to prevent accelerated wear or other damage to the gears.
Due to the critical nature of the worm and gear alignment, consideration to prevent backlash caused by the reciprocating load had to be given. Various shims or gaskets of different thicknesses had to be provided for end cap and bearing adjustment purposes to thereby move the worm relative to the gear for optimum meshing without backlash. These adjustments were highly precise and critical and required skilled workers and substantial time to accomplish the desired purpose.